A Modelling study of hole transport in GaN/AlGaN superlattices

TL;DR

This study models hole transport in GaN/AlGaN superlattices, analyzing how barrier composition and well thickness affect miniband properties and scattering, aiming to optimize hole mobility.

Contribution

It provides a theoretical framework for understanding and optimizing hole transport in GaN/AlGaN superlattices by examining miniband characteristics and impurity scattering effects.

Findings

Ionized impurity scattering significantly degrades hole transport.

Minimizing wavefunction overlap with impurities can improve mobility.

Design strategies to optimize miniband position and width are proposed.

Abstract

The transport of holes through p-doped wurtzite bulk GaN and AlGaN is poor so transport of holes through GaN/AlGaN superlattices has been proposed and investigated theoretically and experimentally with experimental results showing poor transport. The reason for this poor performance is not fully understood. In this paper, the transport of holes in GaN/AlGaN wurtzite crystal superlattices is investigated through theoretical modeling, examining the role of the composition of the Al$_x$Ga$_{1-x}$N barrier regions and the thickness of the GaN quantum wells and the AlGaN barriers in determining the position and width of the heavy hole miniband. To consider the transport of the holes in the miniband we examine the effective mass of the miniband and possible scattering mechanisms. In particular, ionized impurity(II) scattering from ionized acceptors in the barrier regions is investigated as it is deemed to be the dominating scattering mechanism degrading hole transport. The energy position of the miniband relative to the ionized impurities and the wavefunction overlap with the ionized acceptors in the barrier regions is investigated to minimize II scattering. Some designs to optimize hole transport through wurtzite p-doped GaN/AlGaN superlattices to minimize II scattering are proposed.